In recent years, there has been an increase in the number of ischemic diseases affecting the brain and cardiovascular system accompanying aging. Cerebrovascular disorders caused by intracerebral hemorrhage and intracerebral thrombus, such as cerebral infarction, cerebral hemorrhage, cerebral arteriosclerosis and cerebral phlebothrombosis, and brain disorders such as functional brain damage caused by head injury and so forth bring about a shortage of glucose and oxygen used as energy sources for nerve cell activity. Due to the resulting necrosis of nerve cells at the ischemic site, various symptoms are manifest as sequelae of this necrosis, including cerebrovascular dementia and other disorders. In addition, accompanying the increasing proportion of elderly persons in society resulting from prolongation of the average life span, the problem of such diseases as senile dementia of Alzheimer type is becoming a serious problem both medically and socially. In the past, drugs that were developed against these ischemic cerebrovascular disorders and psychoneurotic symptoms accompanying senile dementia consisted primarily of those that mainly increased blood flow to the brain to promote the supply of glucose, oxygen and so forth to the ischemic site. Although these drugs are referred to with obscure expressions such as cerebral circulatory ameliorants, cerebral metabolic activators and cerebral function ameliorants in terms of their action and mechanism, despite being considered to be effective in improving peripheral symptoms such as hynobulia, emotional disorders and behavioral abnormalities, their effects are not clear with respect to improvement of the core symptoms of dementia such as memory disorders. Thus, at present, since there is no drug which is able to effectively treat these diseases, the development of a therapeutic drug is desired that demonstrates more reliable action and effects while also being safe and easy to use.
In response to the present circumstances, the present invention attempts to provide a novel brain cell protective agent that is effective in the prevention and treatment of ischemic brain disorders, cerebral nerve cell disorders and dementia.